Control of Nuclear Spin Interactions in Solid-state NMR by MAS Sideband Manipulation

通过 MAS 边带操作控制固态 NMR 中的核自旋相互作用

基本信息

批准号：
EP/E003052/1
负责人：
Jeremy Titman
金额：
$ 35.15万
依托单位：
University of Nottingham
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2006
资助国家：
英国
起止时间：
2006 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FE003052%2F1
关键词：
Control Nuclear Spin Interactions Solid

项目摘要

Nuclear magnetic resonance (NMR) spectroscopy is one of the most powerful means of determining molecular structure, making significant contributions over the last 25 years to the study of biological molecules, such as proteins. More recently, NMR has also emerged as an important technique for studying complex molecular systems in the solid phase. Examples include membrane proteins, supramolecular assemblies, biological interfaces, polymers, molecular sieves, ionic conductors, nanocomposite materials and catalysts, systems which will underpin a host of scientific and technological developments in the future.Detailed information about molecular structure is obtained from orientation-dependent nuclear spin interactions, such as the chemical shift anisotropy (CSA). Measurements of these can be made from wideline NMR spectra of powdered solids which show singularities corresponding directly to the principal components of the tensor which describes the interaction. However, spectral overlap means that it is often necessary to resort instead to an analysis of the intensities of the rotational sidebands which appear in the magic angle spinning (MAS) spectrum, and this approach has become routine in the case of the CSA. Furthermore, it has been shown recently that analysis of a moderate number (approximately 8 / 10) of spinning sidebands usually gives more reliable results than fitting the wideline spectrum. A relatively low spinning rate is normally required to give this many sidebands, and so many two-dimensional MAS NMR experiments have been developed which separate the sideband manifolds from different sites and further improve resolution. In particular, we have shown how to record spectra in which the sideband intensities are identical to those expected for a sample spinning at some fraction of the actual MAS rate. This CSA amplification experiment represents a new approach to the measurement of spinning sideband intensities and is the starting point for the research programme proposed here.In the course of the research we will broaden the scope of CSA amplification to include other interactions, scaling them to make measurement of the corresponding tensors feasible in situations where conventional methods fail. We will make measurements of CSA parameters in systems which are challenging for conventional methods. We will compare the results with calculated tensors to extract structural information and to make assignments in poorly-resolved MAS spectra. In addition, we will investigate how experiments which use MAS sideband intensities to study molecular dynamics can benefit from the CSA amplification approach.

核磁共振 (NMR) 波谱是确定分子结构的最有力手段之一，在过去 25 年中为蛋白质等生物分子的研究做出了重大贡献。最近，核磁共振也成为研究固相复杂分子系统的重要技术。例子包括膜蛋白、超分子组装体、生物界面、聚合物、分子筛、离子导体、纳米复合材料和催化剂，这些系统将支撑未来的许多科学和技术发展。有关分子结构的详细信息是从方向依赖中获得的核自旋相互作用，例如化学位移各向异性 (CSA)。这些测量可以通过粉末固体的宽线核磁共振谱来进行，这些谱显示出直接对应于描述相互作用的张量的主成分的奇点。然而，光谱重叠意味着通常需要对魔角旋转 (MAS) 光谱中出现的旋转边带的强度进行分析，并且这种方法在 CSA 的情况下已成为常规方法。此外，最近的研究表明，对中等数量（大约 8 / 10）的旋转边带进行分析通常会比拟合宽线频谱提供更可靠的结果。通常需要相对较低的旋转速率才能给出如此多的边带，并且已经开发了许多二维 MAS NMR 实验，这些实验将边带流形与不同位点分开并进一步提高分辨率。特别是，我们展示了如何记录边带强度与以实际 MAS 速率的一部分旋转的样本所预期的边带强度相同的光谱。该 CSA 放大实验代表了一种测量旋转边带强度的新方法，也是此处提出的研究计划的起点。在研究过程中，我们将扩大 CSA 放大的范围以包括其他相互作用，缩放它们以使得在传统方法失败的情况下，可以测量相应的张量。我们将在对传统方法来说具有挑战性的系统中测量 CSA 参数。我们将结果与计算的张量进行比较，以提取结构信息并在分辨率较差的 MAS 谱中进行分配。此外，我们将研究使用 MAS 边带强度研究分子动力学的实验如何从 CSA 放大方法中受益。